<s>
An	O
event	B-Operating_System
flag	I-Operating_System
is	O
a	O
process	O
synchronization	O
primitive	O
in	O
the	O
OpenVMS	B-Operating_System
operating	O
system	O
.	O
</s>
<s>
Wait	O
for	O
event	B-Operating_System
flag	I-Operating_System
( $WAITFR	O
)	O
--if	O
the	O
flag	O
was	O
clear	O
,	O
this	O
would	O
make	O
the	O
process	O
wait	O
until	O
it	O
was	O
set	O
.	O
</s>
<s>
$	O
WFLOR--wait	O
for	O
any	O
of	O
the	O
specified	O
event	B-Operating_System
flags	I-Operating_System
to	O
be	O
set	O
.	O
</s>
<s>
$	O
WFLAND--wait	O
for	O
all	O
the	O
specified	O
event	B-Operating_System
flags	I-Operating_System
to	O
be	O
set	O
.	O
</s>
<s>
Event	B-Operating_System
flags	I-Operating_System
can	O
be	O
either	O
local	O
(	O
per-process	O
)	O
or	O
common	O
(	O
accessible	O
by	O
more	O
than	O
one	O
process	O
)	O
.	O
</s>
<s>
It	O
is	O
also	O
possible	O
to	O
associate	O
the	O
process	O
with	O
up	O
to	O
2	O
sets	O
of	O
common	O
event	B-Operating_System
flags	I-Operating_System
.	O
</s>
<s>
Every	O
potentially	O
time-consuming	O
asynchronous	O
system	O
call	O
(	O
QIO	B-Operating_System
among	O
others	O
)	O
includes	O
an	O
argument	O
specifying	O
the	O
number	O
of	O
an	O
event	B-Operating_System
flag	I-Operating_System
to	O
set	O
on	O
completion	O
.	O
</s>
<s>
Compare	O
semaphore	B-Operating_System
.	O
</s>
